1. Field of the Invention
This invention relates to a display device, and more particularly to a display device for displaying an image formed by moving liquid impregnated in a porous body by the action of an electric field.
2. Description of the Related Art
There has been known a display device for displaying an image formed by moving liquid impregnated in a porous body by the action of an electric field. For example, there has been known a display device in which an electric voltage is imparted to a porous body impregnated with light transmission liquid material to control the light transmission liquid material pick-up of the porous body surface by the movement of the light transmission liquid material according to the electric voltage, thereby controlling the refractive index of the porous body surface. See, for example, Japanese Unexamined Patent Publication No. 55(1980)-70820. In this display device, when the porous body surface is fully impregnated with light transmission liquid material, the refractive indexes of the porous body and the light transmission liquid material are substantially equal to each other, whereby the external light is not reflected by the interface therebetween but is transmitted through the interface, whereas when the light transmission liquid material pick-up of the porous body surface is reduced, vacant porosities are generated in the porous body surface, whereby non-uniformity in refractive index is caused between the air in the porosities and the material of the porous body and the external light is reflected by the interface therebetween.
However, in such a display device where the reflectance of the surface of a porous body is controlled by moving light transmission liquid material impregnated in the porous body to change the light transmission liquid material pick-up of the porous body surface, there has been a problem that, since the range of movement of the liquid is limited, the liquid pick-up of the porous body surface does not sufficiently change, whereby high contrast cannot be obtained in display.